The present invention relates to the field of the operation of integrated circuits; and more particularly, relates to the adaptation of integrated circuits to work with power supplies having incompatible configurations and/or voltage levels. In both cases, the incompatibility is overcome by using voltage level translation.
In consumer electronics where low cost is an important engineering parameter, it is not uncommon to design using low cost parts in a manner in which the part was not designed to be used. Such a case can be where the power supply for a device has been designed for other purposes and it becomes necessary to use this seemingly incompatible power supply for providing an auxiliary feature. Such a case can be for a DVD player where the power supply is a balanced split level power supply, i.e., xc2x15.0 volts with a center tapped ground, and it is desirable for cost reasons to use an integrated circuit which is designed for a single ended power supply with input and output coupling capacitors, which are desirable to eliminate. Such input and output coupling capacitors represent an extra parts cost and also can take up printed circuit board space which sometimes is very limited. Moreover, if the input and output capacitors are electrolytics, they are particularly larger than other capacitors and represent an additional reliability problem which is desirable to eliminate.
Additionally, the incompatibility of power supply and integrated circuit configurations can occur in, for example, a digital circuit system, where various subsystems operate with different power and voltage requirements. Some integrated circuit protocols and systems require a supply voltage with a Vcc (the positive rail voltage) of 3.3 volts and a Vss (the lower rail voltage) of ground potential, while others may require a Vcc -to-Vss voltage of 5.0 volts or 2.9 volts.
Still further concerning incompatible voltages available from a power supply, many integrated circuits are extremely sensitive to over-voltage or over-current, since such overages can not only provide incorrect results (particularly if the integrated circuit is digital) but can also cause physical damage to the integrated circuit. Most processors have voltage and current ratings that may not be exceeded by even a little bit without causing severe damage to the integrated circuit. For example, it is not uncommon for microprocessors designed for operating at a power supply voltage of 3.3 volts to be damaged by application of signals in excess of a peak to peak of 3.45 volts when reading data from RAMs in which the high/low voltage differential is 5.0 volts. Therefore, closely limiting the voltage supply levels to meet specification is essential to the operation of integrated circuits.
A first embodiment of a voltage level translator is presented for operating an operational amplifier integrated circuit designed for operation with a single ended power supply, to operate with a split level power supply having a center tapped ground. A first polarity power supply terminal of a operational amplifier integrated circuit is connected to a first polarity of the of the split level power supply, and a second polarity power supply terminal of the operational amplifier integrated circuit is connected to an second polarity of the power supply, with a signal input terminal of the operational amplifier being connected to the center tapped ground.
A second embodiment of a voltage level translator is presented to permit an integrated circuit having a predetermined maximum voltage rating to be operated with split level power supply having a power supply voltage greater than the voltage rating, wherein a first voltage translation zener diode is coupled in series between a first polarity of the power supply and an appropriate first polarity terminal of the integrated circuit, and a second voltage translation zener diode is coupled in series between a second polarity of the power supply and an second polarity terminal of the integrated circuit,